A　universal　and　facile　electrochemical　etching　method　for　synthesizing　nanosized　metal　oxide　semiconductors　has　been　presented　by　taking　the　synthesis　of　ZnO　quantum　dots　(QDs)　from　metallic　zinc　as　an　example.　By　applying　an　appropriate　potential,　metallic　zinc　was　controllably　oxidized　to　Zn2+　ion,　the　latter　(Zn2+)　was　released　into　an　organic　electrolyte　and　hydrolyzed　by　trace　dissolved　water　therein.　giving　rise　to　ZnO　QDs.　The　electrochemically　synthesized　ZnO　QDs　were　uniform　particles　with　an　average　diameter　of　5.0　nm.　and　exhibited　good　photoluminescent　and　electrochemiluminescent　activities.　The　effects　of　applied　potential　window,　amount　of　water　and　dissolved　oxygen　on　the　formation　of　ZnO　QDs　were　investigated　and　discussed　in　detail.　The　presently　proposed　electrochemical　etching　method　not　only　has　provided　a　facile,　low-cost　and　controllable　way　to　obtain　ZnO　QDs,　but　also　would　be　applicable　as　a　universal　method　in　synthesizing　other　kinds　of　nanosized　metal　oxide　semiconductors　from　related　metals.　(C)　2010　Elsevier　Ltd.　All　rights　reserved.